Well the drawbacks it states pretty clearly:
Unfortunately, there are more drawbacks than benefits; the longer the user has this jutsu active, the more at risk he is of fatally harming himself from the reverted flow of chakra. If active for longer than two turns, upon deactivation the user can only use taijutsu attacks for two turns as it takes time for the user's tenketsu to start it's correct flow. The user also can not use any Keigoku techniques of S-rank and higher while this is active. While this is active, the user is vulnerable to sealing jutsus that seal away elements and/or jutsus.
But to me, a Tai enthusiast, them two turns of all Tai would be a walk in the park. Also the disadvantage is if anyone could prevent S/T techniques.... looks at a particular piratey mod... we couldn't use this. Could possibly even get stuck in the portals if something was used to prevent S/T techs after we entered the portals.
And now, for the infamous Way of Destruction Number Ninety: Black Coffin. Creates their coffin by creating portals all around the enemy, the last one on the bottom forming last. I remember the first time Broly used this one on me lol. Awesome technique, I'd use this after using something to immobilize the enemy, perhaps a paralyzing genjutsu for example, to make time for the bottom portal to form to making escape that much harder. Once formed, spears form on the walls shooting outwards impaling them in a keigoku iron maiden! Only disadvantages are the time it takes the bottom portal to form, and that Nekura techs above A rank can't be used during the turn or the next
